The present invention relates to the manufacture of yarn and, more particularly, relates to the coating or dyeing of yarn traveling at high speed.
The process of weaving yarn into fabrics often damages the yarns. To prevent damage, a protective coating is typically applied to the surface of the yarn prior to weaving. This protective coating is typically applied as a liquid solution called size or sizing. The application of size is commonly referred to as slashing. However, the application of sizing is time consuming which results in significant delays in the manufacture of yarns suitable for weaving.
In known methods of applying sizing, a sheet of closely spaced yarns are slashed by passing the sheet of yarns through an aqueous solution of sizing. Typically, the sheet of yarn has a residence time of 0.25 seconds, or greater, in the solution. The sheet of yarns is then squeezed by high pressure rollers that drive the sizing into the sheet of yarns. However, the sizing is often not distributed uniformly over each yarn.
Next, the sheet of yarns is dried by passing it over a heated drum which produces a solid sheet of yarns held together by the dried sizing. The yarns of the sheet are then separated by passing them over and under lease rods. Separating the yarns in this manner, however, causes damage to the yarns. Fibers are often broken and left protruding from the surface of the yarn as a result of this separation process. This creates a hairy yarn which is undesirable. If the yarns did not need to be separated after sizing, this damage would not occur.
There are techniques known for applying treatments such as chemical coatings or dyes to individual yarns. These known techniques apply the treatments by passing each yarn, traveling at low speed, through an opening such as an eyelet or slot having sides configured for applying the treatment and to prevent the yarn from jumping out. Typically, the process of making rows of yarn, referred to as beams, run at speeds as high as approximately 1,000 yards per minute. With traditional methods of slashing individual yarns or sheets of yarn, however, the run speed has to be reduced to below 100 yards per minute. Moreover, the sizing is applied intermittently to the individual yarns and, therefore, is not applied in a uniform manner.
Also, these known techniques attempt to achieve uniform application by the manner in which the treatment is introduced to the yarn. None of these known techniques facilitate the application of the treatment in a substantially uniform manner to yarn advancing at speeds above 100 yards per minute.
Therefore, there is a need for a new slashing method to optimize the application of sizing when the yarns are advanced at high speed. This new slashing method applies sizing to each yarn separately in a metered fashion for uniform application eliminating the separation process described above. The yarn is sized in a fast and cost effective manner without the resulting yarns having a hairy surface.
The present invention solves the above-identified problem by providing an improved apparatus for single-end slashing. This improved apparatus includes an optimally configured slot to facilitate the uniform application of sizing to individual yarns advancing at high speed.
Generally described, the present invention includes a slot applicator having at least one slot for receiving an individual yarn. Fluid is metered into the slot as the yarn advances through the slot. The slot has an extended length dimensioned for affecting the distribution of the fluid on the advancing yarn. In particular, the length of the slot is dependent on the speed of the advancing yarn. The length creates additional contact between the advancing yarn and the metered fluid.
According to one aspect of the present invention, the advancing yarn has a predetermined residence time in the slot. The required residence time is a function of yarn construction, fiber type, fluid properties and yarn speed.
The foregoing has broadly outlined some of the more pertinent aspects and features of the present invention. These should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Other beneficial results can be obtained by applying the disclosed information in a different manner or by modifying the disclosed embodiments. Accordingly, other aspects and a more comprehensive understanding of the invention may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings, in addition to the scope of the invention defined by the claims.